Critical and Triple Points of Films of Quantum Gases

Abstract

We report heat capacity measurements of monolayer films of 4He adsorbed on very uniform MgO, a substrate of square symmetry, for 0.5 K < T < 2.5 K, and vapor pressure measurements on H2 multi-layer films adsorbed on the same substrate, for 8.6 < T < 28 K. The low density 4He films data show a peak at T = 1 K that may signal liquid-vapor condensation. The bilayer H2 film vapor pressure data show two-phase coexistence regions that can be interpreted as liquid-vapor and solid-vapor coexistence. We deduce that for the bilayer film Tt=7.6 K and Tc=10.5 K. All critical and triple point temperatures fall closely within expectations from the quantum theorem of corresponding states.